Introduction
Specific gravity tells you how heavy a material is compared to water. If something has a specific gravity less than 1, it floats. If it is greater than 1, it sinks. This simple ratio has no unit because it is just one density divided by another.
This specific gravity calculator lets you work in two directions. You can enter a known density to find the specific gravity, or enter a known specific gravity to find the density. It supports many mass and volume units, so you can work in metric or imperial without doing conversions by hand.
You can also change the reference water temperature. Water is densest at 4°C, and most standard specific gravity values use that temperature. But if your work uses a different temperature, this tool adjusts the water density for you using an accurate model.
The calculator shows a step-by-step solution, a visual scale, and a comparison chart so you can see how your result stacks up against common substances like gasoline, seawater, mercury, and gold. You can also click any row in the reference table to load that substance instantly.
How to Use Our Specific Gravity Calculator
Enter a density or specific gravity value, and this calculator will convert it for you. It also shows if your material floats or sinks in water.
Pick a conversion mode. Click "Density → Specific Gravity" if you know the density and want to find the specific gravity. Click "Specific Gravity → Density" if you know the specific gravity and want to find the density.
Enter your density value (Density → SG mode). Type the density number into the input box. Then choose the correct mass unit and volume unit from the dropdown menus to match your number.
Enter your specific gravity value (SG → Density mode). Type the specific gravity number into the input box. Specific gravity has no unit because it is a ratio. Then pick your preferred output density unit from the dropdown menu.
Set the water reference temperature (optional). The default is 4 °C, which is the standard. Change this only if your work uses a different reference temperature. Click the °C / °F button to switch between Celsius and Fahrenheit.
Load a preset substance (optional). Pick a common material like seawater, gasoline, or gold from the dropdown list. The calculator will fill in the specific gravity value for you automatically.
Click "Calculate" to see your result. The answer appears on the right along with a float-or-sink indicator, a step-by-step solution, a visual scale, and a comparison chart. Click "Reset" at any time to clear all inputs and start over.
What Is Specific Gravity?
Specific gravity is a number that tells you how heavy a material is compared to water. It has no unit because it is a simple ratio. You find it by dividing the density of a material by the density of water. If the answer is exactly 1, the material is just as heavy as water. If it is less than 1, the material is lighter than water and will float. If it is greater than 1, the material is heavier than water and will sink.
How to Calculate Specific Gravity
The formula is straightforward:
Specific Gravity = Density of Material ÷ Density of Water
Water's density changes slightly with temperature. At 4°C (39.2°F), water is at its densest, about 999.97 kg/m³. This is the standard reference point most scientists and engineers use. Our calculator lets you change the reference temperature if your work requires it, and it uses the Kell equation to find the exact water density at that temperature.
Why Specific Gravity Matters
Specific gravity is used in many fields. Brewers use it to track fermentation. Geologists use it to identify minerals. Engineers use it to pick the right materials for ships and pipelines. Doctors use it to check urine samples. Oil companies use it to grade fuels like gasoline and diesel. Because specific gravity is a ratio with no units, it works the same no matter what measurement system you use, metric or imperial.
Density vs. Specific Gravity
Density tells you how much mass fits in a certain volume, like kilograms per cubic meter. Specific gravity removes the units by comparing that density to water. This makes it easy to compare materials quickly. For example, gold has a specific gravity of 19.3, which means it is 19.3 times heavier than the same volume of water. Gasoline has a specific gravity of about 0.74, so it floats on water.
How to Use This Calculator
This calculator works in two directions. In the first mode, you enter a known density with its mass and volume units, and the tool gives you the specific gravity. In the second mode, you enter a known specific gravity, and it gives you the density in your chosen unit. You can also load preset substances like seawater, honey, or mercury to see their values instantly. The calculator shows a step-by-step solution, a visual scale, and a comparison chart so you can see exactly where your material falls relative to water and other common substances.